Dense chrome refractory material

ABSTRACT

A dense chrome refractory material having superior corrosion resistance to molten glass has been prepared, said refractory comprising from 85 percent to 98 percent chromic oxide, from 1 percent to 10 percent zircon and from 0.5 percent to 5 percent of a titanium compound selected from the group consisting of barium titanate and titanium dioxide.

United States Patent [1 1 Manigault [21] Appl. N0.: 271,604

[52] U.S. Cl. 106/57, 106/66 [51] Int. Cl. C04b 35/12, C04b 35/16 [58]Field of Search 106/57, 66

[56] Reierences Cited UNITED STATES PATENTS 2,498,622 2/1950 Mochel106/66 1 Nov. 20, 1973 Steijn 106/66 Thomas 106/66 PrimaryExaminer-James E Poer AttorneyRobert L. Leham et a1.

[5 7] ABSTRACT A dense chrome refractory material having superiorcorrosion resistance to molten glass has been prepared, said refractorycomprising from 85 percent to 98 percent chromic oxide, from 1 percentto 10 percent zircon and from 0.5 percent to 5 percent of a titaniumcompound selected from the group consisting of barium titanate andtitanium dioxide.

7 Claims, No Drawings 1 DENSE CHROME REFRACTORY MATERIAL BACKGROUND OFTHE INVENTION Chrome refractories have been used in the past in theglass industry. Such chrome refractories however, suffered from thedisadvantages of being relatively porous and therefore subject to highcorrosion attacks. Improvements have been made recently in the chromerefractories by employing small quantities of barium titanate which inturn decreased the porosity and increased the corrosion resistance ofthe chrome refractory material.

It has now been found, however, that a dense chrome refractory having avery low porosity and high corrosion resistance has been produced whichis superior to the chrome refractories previously produced.

It has also been found that the new type of chrome refractory may beproduced without the tendency to crack and split during firing which wasvery difficult to prevent with the prior art chrome refractorycompositions.

SUMMARY OF THE INVENTION A dense chrome refractory material has beenproduced comprising from 85 percent to 98 percent chromic oxide, from 1percent to 10 percent zircon and from 0.5 percent to 5 percent of atitanium compound selected from the group consisting of barium titanateand titanium dioxide. This refractory material possesses very lowporosity, has high corrosion resistance to molten glass, and inaddition, has good resistance to thermal cracking during firing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In preparing the chromerefractory material of the instant invention, all of the ingredientsshould be ground to --325 mesh.

The chromic oxide used in the refractory composition should be of highpurity, i.e., preferably the socalled technical" grade chromic oxidehaving a purity of at least 97 percent.

In preparing the refracotyr blocks, the ceramic mixture is formed byadmixing the chromic oxide with from 1 percent to percent zircon andfrom 0.5 percent to 5 percent barium titanate or titanium dioxide, thepercentages based on the weight of the chromic oxide.

Blocks are formed from the mixture by either slip casting or isostaticpressing the mixture into the form of blocks and firing the blocks at atemperature between l500C and 1650C, preferably between 1560C and 1600C.If the slip casting process is used, it is usually necessary to add asmall amount of deflocculating agent when forming the slip-cast pieces.

The blocks formed possess very low porosity, and high corrosionresistance to molten glass. In addition, they are very resistant towardcracking during firing.

Chrome refractory blocks produced by the prior art commonly developcracks on the bottom surface of the block where they contact the settertile. This cracking probably is due to the movement caused by the bottomface shrinkage and its dragging across the setter tile.

tween the particles at the temperature where the shrinkage occurs.

' w hen thecfirorneblocks are made having the composition of the instantinvention, these cracks do not develop in the block despite the factthat their firing shrinkage is substantially identical to the prior artchrome blocks described above.

In order to describe the instant invention more fully,

the following examples are presented:

EXAMPLE 1 In this example kg of technical grade chromicoxide, having apurity of 98.5% Cr O were mixed with 3 kg of zircon and 2 kg of bariumtitanate. All of the ingredients were ground to 325 mesh. The mixturewas dry blended for 3 minutes. 3 kg of a 5 percent aqueous solution ofan alkyl-phosphate lubricant were added to the mixture and the mixturewas then wet blended for 8 minutes.

Blocks 3 56 X 5 X 18 inches were isostatically pressed at 15,000 psi anddecompressed at 3 minutes per inch of block thickness, based on thegreen size. The pressed blocks were then air dired for one week.

The dried blocks were then set on end in a kiln, protected by a 3 inchbagwall and fired at 1593C at 18C rise per hour and were held at thattemperature for 8 hours. After heating, the blocks were allowed to coolat a rate of 28C per hour until a temperature of 93C was reached whenthey were removed from the furnace.

The fired blocks were examined and possessed the following properties:

Porosity 1.0 percent Absorption 0.2 percent Bulk Density 4.56 g/ccTendency to Crack None The blocks were then subjected to a corrosiontest in which the blocks were cut into a rectangular test bar 1hcmbyllcmby 10cm.

The test bar was then submerged to a depth of 3 cm along the 10 cmdimension in a molten glass batch (fiber glass type) which had beenheated to 2700F and the test bar was held in the molten bath for hours.

After removal from the molten glass, the extent of corrosion was foundby comparing post-test measurements with the original measurements. Themeasurements were taken at the junction of the glass surface and thetest bar (called the metal line), at 1 cm below and at 0.5 cm above themetal line. The change in measure-ments were recorded as the amount ofcorrosion which took place.

The loss in length at its metal-line was 0.34 mm while the loss 1 cmbelow the metal line was 0.10 mm and 0.5 cm above the metal line was0.16 mm.

EXAMPLES 2-5 Again in all of the examples, improved results were"obtained. The results along with the controls are presented in thefollowing table:

Examples Prior 1 2 3 4 5 Control art Chromic oxide, kg 95 93 91 95 92100 98 Zircon, kg 3 5 7 3 5 0 Barium titanate, kg. 2 2 2 O 3 0 2Titanium dioxide, kg". 0 0 0 2 0 0 0 Porosity, percent 1.0 1.36 0.3 0.33.4 44.0 5. 0 Absorption, percent 0.2 0.3 0.1 0.1 0.7 15.2 1.0 Bulkdensity, gm./ce- 4. 56 4.48 4.3 4.63 4. 57 2.9 4.76

EXAMPLES Con- Prior Tendency 1 2 3 4 trol Art to crack none-lone nonenone none badly badly EXAMPLES Prior Corrosion 1 2 3 Art Metal-lineloss, mm 0.34 0.33 0.35 0.36 Loss I cm below metal line, mm 0.10 0.090.12 0.15 Loss 0.5 cm above metal line, mm 0.16 0.17 0.17 1.19

From the above data, it has clearly been shown that the blocks made withthe combination of zircon and titanium compound possessed lower porosityand absorption than blocks which contained no zircon. In addition thecorrosion loss was less in the examples employing the composition of theinstant invention than that obtained by the prior art chrome refractory.Also there was no tendency for the refractories of the instant inventionto crack while those of the prior art cracked readily.

While this invention has been described and illustrated by the examplesshown, it is not intended to be strictly limited thereto, and othervariations and modifications may be employed within the scope of thefollowing claims.

1 claim:

1. A dense chrome refractory composition comprising from percent to 98percent chromic oxide, from 1% to 10% zircon and from 0.5 percent to 5percent of a titanium compound selected from the group consisting ofbarium titanate and titanium dioxide.

2. Composition according to claim 1 in which the titanium compoundemployed is barium titanate.

3. Composition according to claim 1 in which the titanium compoundemployed is rutile titanium dioxide.

4. A method for the preparation of a dense chrome refractory compositionwhich comprises admixing chromic oxide, zircon and a titanium compoundselected from the group consisting of barium titanate and titaniumdioxide, the amount of chromic oxide being from 85 percent to 98percent, the amount of zircon being from 1 percent to 10 percent and theamount of the titanium compound being from 0.5 percent to 5 percent, allof the percentages being expressed by weight, forming said mixture intoa shaped body and firing the body at a temperature from 1500C to 1650Cto form the refractory composition.

5. Method according to claim 4 in which the shaped body is fired at atemperature from 1560C to 1600C.

6. Method according to claim 4 in which the titanium compound employedis barium titanate.

7. Method according to claim 4 in which the titanium compound employedis rutile titanium dioxide.

2. Composition according to claim 1 in which the titanium compoundemployed is barium titanate.
 3. Composition according to claim 1 inwhich the titanium compound employed is rutile titanium dioxide.
 4. Amethod for the preparation of a dense chrome refractory compositionwhich comprises admixing chromic oxide, zircon and a titanium compoundselected from the group consisting of barium titanate and titaniumdioxide, the amount of chromic oxide being from 85 percent to 98percent, the amount of zircon being from 1 percent to 10 percent and theamount of the titanium compound being from 0.5 percent to 5 percent, allof the percentages being expressed by weight, forming said mixture intoa shaped body and firing the body at a temperature from 1500*C to 1650*Cto form the refractory composition.
 5. Method according to claim 4 inwhich the shaped body is fired at a temperature from 1560*C to 1600*C.6. Method according to claim 4 in which the titanium compound employedis barium titanate.
 7. Method according to claim 4 in which the titaniumcompound employed is rutile titanium dioxide.